Berberine inhibits the progression of breast cancer by regulating METTL3-mediated m6A modification of FGF7 mRNA.

Background: Berberine (BBR), an isoquinoline alkaloid from Coptidis rhizoma, has been found to have powerful activities against various human malignancies, including breast cancer. However, the underlying antitumor mechanisms of BBR in breast cancer remain poorly understood.

Methods: Breast cancer cells were cultured and treated with different doses (0, 20, 40, and 60 μM) of BBR for 48 h. Cell viability, proliferation, apoptosis, invasion, and migration were assessed using 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2H-tetrazolium bromide (MTT), 5-ethynyl-2'-deoxyuridine (EdU), flow cytometry, transwell, and wound healing assays. Fibroblast growth factor 7 (FGF7), methyltransferase-like 3 (METTL3), and insulin-like growth factor-2 mRNA-binding protein 3 (IGF2BP3) mRNA levels and protein levels were measured using real-time quantitative polymerase chain reaction (RT-qPCR) and western blot. Interaction between METTL3 and FGF7 m6A was assessed using methylated RNA immunoprecipitation (MeRIP)-qPCR and RNA immunoprecipitation (RIP) assay. Binding ability between IGF2BP3 and FGF7 mRNA was analyzed using RIP assay.

Results: BBR treatment hindered breast cancer cell proliferation, invasion, migration, and induced apoptosis. FGF7 expression was upregulated in breast cancer tissues, while its level was reduced in BBR-treated tumor cells. FGF7 upregulation relieved the repression of BBR on breast cancer cell malignant behaviors. In mechanism, METTL3 stabilized FGF7 mRNA through the m6A-IGF2BP3-dependent mechanism and naturally improved FGF7 expression. BBR treatment inhibited breast cancer growth in vivo.

Conclusion: BBR treatment blocked breast cancer cell growth and metastasis partly by regulating METTL3-mediated m6A modification of FGF7 mRNA, providing a promising therapeutic target for breast cancer treatment.